I have long suggested the purchase of PDF Expert by Readdle–it is the best PDF manager that I know of (for the iPad). This isn't an app for your music PDF files, but it is an app for all the other PDF documents that come into your life. I have used the app for everything from signing contracts and personal bank documents to applying to present at conferences.
I had been using the old version of PDF Expert (4th version), but a new version was released in late 2013–but Readdle required you to purchase the new version (this is understandable, as companies cannot continue to update an app for free forever). I was going to wait until the app went on sale before I bought it.
Over the last months, Readdle has offered sales on many apps–including offering some for free–but PDF Expert 5 has never been on sale before. It is on sale right now for 50% off, and yes, I bought it this morning. This is a 48 hour–so the 50% sale will not last long. This is one of those “front page apps” on my iPad, and it will likely be the same on yours. Don't miss the sale!